Takaya Wada

2GHz band quadruple mode dielectric resonator filter for cellular base station

This paper describes a novel 2GHz bandpass filter using a novel quadruple mode dielectric resonator for compact cellular base station. We propose small high Q dielectric resonator technique using TM/sub 11//spl delta/-x, TM/sub 11//spl delta/-y, TE/sub 01//spl delta/-x and TE/sub 01//spl delta/-y modes. It has very high unloaded Q factor value of about 15000 at 2GHz band. We have designed and manufactured a 4-pole band filter using this resonator. Insertion loss is very low of less than 0.23 dB and high attenuation of 90dB. Outer dimensions are 48 /spl times/ 48 /spl times/ 42 mm.

A new tunable filter using love wave resonators for reconfigurable RF

A large number of frequency bands have been included in mobile phone handsets and in their RF front end circuit, RF paths have been increasing and the configuration has been becoming complex more and more. A new tunable filter is proposed in this paper. In order to realize a wide bandwidth SAW resonator using extension inductor, Love wave SAW resonator for the tunable filter can be obtained by the optimization of the Euler angle and Pt film thickness to avoid Rayleigh wave spurious and the bulk wave. A tunable filter is fabricated for the operation in the low frequency band of 669-960MHz which fractional bandwidth is 31.5%. This result shows promising possibility of a tunable filter for reconfigurable RF.

A new tunable RF front-end circuit for advanced 4G handsets

A large number of frequency bands have been included in mobile phone handsets and in their RF front end circuit, RF paths have been increasing and the configuration has been becoming a complex more and more. A new tunable RF front-end circuit for single RF chain architecture is proposed in this paper. A tunable duplexer composed of wideband circulator and SAW based tunable filters for TX and RX, and a tunable low RX noise power amplifier have been developed. RX band noise level in FDD system is studied. Those devices are fabricated for the operation in the low frequency band of 669-960MHz which fractional bandwidth is 31.5%. Experimental results in Band 5 and Band13 show 40dB isolation of the tunable duplexer and 10dB noise level improvement of the tunable low RX noise PA, which achieve target value of 50dB suppression of RX band noise. This results show promising possibility of simple RF front-end of future mobile handsets.

A miniaturized broadband lumped element circulator for reconfigurable front-end system

A novel miniaturized broadband circulator for reconfigurable mobile handsets has been successfully developed. The circulator operating in a weak magnetic field below ferromagnetic resonance is derived by analyzing the equivalent circuit. The operating theory of the circulator has been confirmed by using the perturbation theory. The usable isolation band could be expanded to 1.71GHz to 2.17GHz, which is a very small sized 1.2 × 1.0 × H0.5 mm3 such as 1/25 compared with the conventional one, Core-Circulator is realized. The developed circulator keeps characteristics as the insertion loss of 1.1dB maximum and the TX-RX isolation of 21dB minimum which have achieved the requirements of the tunable RF front-end.

A new tunable SAW filter circuit for reconfigurable RF

In recent years, the mobile data traffic is increasing and many more frequency bands have been employed in cellular handsets. A simple π type tunable band elimination filter (BEF) with switching function has been developed using a wideband tunable surface acoustic wave (SAW) resonator circuit. The frequency of BEF is tuned approximately 31% by variable capacitors without spurious. In LTE low band, the arrangement of TX and RX frequencies is to be reversed in Band 13, 14 and 20 compared with the other bands. The steep edge slopes of the developed filter can be exchanged according to the resonance condition and switching. With combining the TX and RX tunable BEFs and the small sized broadband circulator, a new tunable duplexer has been fabricated, and its TX-RX isolation is proved to be more than 50dB in LTE low band operations.

Investigations on design technologies for SAW quadplexer with narrow duplex gap

Carrier aggregation (CA) is an inevitable technology to improve the data transfer rate with widening operation bandwidths, while the current frequency assignment of cellular bands is dispersed over. In the frequency division duplex (FDD) CA, acoustic multiplexers are one of the most important key devices. This paper describes the design technologies for the surface acoustic wave (SAW) multiplexers, such as filter topologies, matching network configurations, SAW characteristics and so on. In the case of narrow duplex gap bandwidth such as Band4 and Band25, the characteristics of SAW resonators such as unloaded quality factor (Q) and out-of band impedances act as extremely important role to realize the low insertion loss and the steep skirt characteristics. In order to solve these challenges, a new type high Q SAW resonator that is named IHP-SAW is introduced. The results of a novel quadplexer of Band4-Band25 using those technologies show enhanced performances.

Tunable isolator using variable capacitor for multi-band system

A novel tunable isolator for multi-standard mobile handsets has been successfully developed. A new circuit configuration for tuning operation frequency of the isolation is proposed. It shows that the isolation band is tuned widely by varying the variable capacitor value without increasing the insertion loss. A 1.5 × 0.9 × H0.4mm3 Core-Isolator and a 0.5 × 0.5 × 0.2mm3 (BaSr)TiO3 (BST) variable capacitor have been fabricated on a PCB. By using this circuit, usable isolation band could be expanded to 698-915MHz, which is 6 times wider than conventional one. The developed isolator keeps other characteristics such as 0.6dB max of insertion loss, 12dB min of isolation and -60dBc level of ACLR (5MHz).

28 GHz wideband filter using quartz crystal waveguide for massive MIMO antenna unit

Massive MIMO technology and mm-wave band radio communication are effective solution of a high data rate for 5G. This paper presents a novel 28GHz wideband filter for those antenna units. To realize a wide fractional bandwidth of 10%, a new terminal configuration of “Y-shaped” structure is proposed. A TEM-TE mode transition function using the new structure was analyzed, and the shape was optimized. Applying the new terminal structure to an 8-pole with 2 trap quartz waveguide filter, high performances such as very low loss of 1.2 dB, wide relative passband of 10.4% and high attenuation of more than 50dB were obtained with a small size and SMD structure.

A novel switchable SAW Duplexer for band 28

Band 28 has wide bandwidth of 45MHz and narrow duplex gap of 10MHz in 700MHz band, and since digital terrestrial TV channels in some countries are overlapped with lower frequency range of the uplink band, two types of duplexer which have slightly shifted passbands need to be used. This paper describes a novel switchable SAW duplexer which can cover both bands in one duplexer. By using a filter design technique with unique switching circuit, and wideband and low temperature drift SAW resonator technology, high performance such as 2.6/3.0dB insertion loss and 55dB isolation have been achieved, in addition to more than 13/16dB near point attenuation only 5/8MHz apart from the passband edge. The developed switchable duplexer can lead the reduction of 40% in mounting area on RF front-end circuit of mobile terminals.

A study on low Rx-band noise power amplifier for reconfigurable RF front-end circuit

RF paths in mobile phone have been increasing and the configuration has been becoming a complex year by year. A new tunable RF front-end circuit for a single RF chain architecture was proposed. That solution needs the tunable low RX-band noise power amplifier(LNPA) in order to reduce the noise at a RX input port of a transceiver IC in cooperation with the tunable duplexer in FDD system handsets. In this paper, a principle of LNPA is described and it is shown that an interstage filter is effective compared with other circuit configulations. The required characteristics for the interstage filter in LNPA are studied and the RX band attenuation of the interstage filter is calculated with employing equations using noise figure and gain parametaers. It is found that the RX-band noise floor of LNPA is determined by the noise level of a back stage amplifirer Q2, when the interstage filter RX band attenuation is more than 25dB. LNPA is fabricated to clarify the operation and less than -140dBm/Hz which is the target value of the system can be obtained. This results show the promising possibility of Tunable LNPA for simple RF front-end for future mobile handsets.